The present invention relates to the addition of aqueous solutions of zinc ammonium complexes to water based coating compositions to provide a stain-blocking primer composition and to provide a mildewcide and/or biocide resistant coating composition.
In the past, various types of materials have been suggested to be added to water based coating compositions to provide a stain-blocking primer composition. For example, U.S. Pat. No. 3,852,087, disclose the addition of amphoteric compounds, such as, the hydroxides or hydrates of alumina, titania, zirconia, silica or zinc to water based paints to render the tannins insoluble and to prevent their migration through the paint film.
Additionally, U.S. Pat. No. 3,969,293 discloses the use of tribasic zinc phosphites as a substitute for lead in latex paint formulations to provide a pigment which possesses tannin stain-blocking properties and which may possess mildew preventive properties. However, such paint formulations require excessive amounts of zinc oxide in the paint formulations which facilitate cross-linking of the film which causes cracking of the deposited films after extended applications.
Also, U.S. Pat. No. 4,031,055 discloses latex coating compositions containing compounds of zinc which possess improved mildew resistance when such compositions contain isothiazolone type compounds as the mildew controlling material. However, such compositions do not possess stain-blocking properties and do not possess the required long term mildewcide properties of five years and beyond that is required of commercially acceptable coating compositions. Also, the attendant costs associated with the use of large amounts of zinc oxide in such compositions to provide long term mildewcide properties limit the usage of such compositions.